1. Field of the Invention
The present invention relates to a remote control system which controls devices connected to a wireless network.
2. Description of the Related Art
ZigBee is a new standard of a remote control system which aims for building/home automation through a low-cost and low-power device used for a few years with two AA alkaline batteries. In such ZigBee, a radio frequency of 2.4 GHz band is divided into 16 channels and used. 255 devices (devices to be controlled) can be connected per network. Data can be transferred at speeds up to 250 kbps within 30 m. Such ZigBee has the feature that although the rate of the data is low as compared with the recent wireless LAN or the like, power consumption can be reduced far low owing to ZigBee.
The standard of ZigBee is still in the draft stage. According to the draft, however, a network forms a PAN (Personal Area Network) wherein respective devices are connected in a tree structure with a coordinator as the center. Connections between the coordinator and the respective devices by radio are defined or provided such that the connections are performed by a CSMA-CA (Carrier Sense Multiple Access with Collision Avoidance) system through the use of a super frame having a frame beacon and time slots, and the establishment of their connections is carried out in accordance with processes at a network layer and a MAC (Machine Address Code) layer.
Specific example applications for ZigBee widely range from control of illumination and television to a home security system in homes. A network capable of controlling all by wireless can be constructed with respect to them. Thus, there is a possibility that an infrared interface such as a remote controller (hereinafter called “remocon”) for conventional television will be able to be perfectly substituted with one integrated network.
When a large number of devices are connected in practice, although the 255 devices can be connected per network in ZigBee, the individual execution of control on these devices becomes burdensome to ZigBee. As a simple method for controlling a device, may be mentioned, a method using a remocon dedicated to the device. Remocons for television, an air conditioner, a video cassette recorder, etc. are widely ubiquitous even at present. However, ZigBee is intended for all devices at home such as an illuminating device, a warning device, a refrigerator, a toy, a body of a personal computer and a mouse, a keyboard, etc. in addition to the television or the like. They have been diversified in function too. Thus, the individual fabrication of remocons for these devices could cause a situation flooded with the remocons throughout the house.